Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 020359
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
859 PM PDT SUN MAY  1 2016

.SYNOPSIS...A STRONG UPPER HIGH WAS CENTERED OVER SOUTHWEST CANADA
THIS EVENING AND WILL CONTINUE TO BRING WARM DRY WEATHER WITH SOME
OFFSHORE FLOW TO SOUTHWEST WASHINGTON AND NORTHWEST OREGON INTO
MONDAY. THE PATTERN WILL BEGIN TO BREAK DOWN MONDAY AFTERNOON AS A
PACIFIC FRONT SLOWLY APPROACHES THE COAST. MOISTURE AND INSTABILITY
WILL SPREAD NORTHWARD INTO THE FORECAST AREA LATE MONDAY AND MONDAY
NIGHT INTO TUESDAY UNDER DEVELOPING SOUTHERLY FLOW ALOFT. COOLER
MARINE AIR WILL SPREAD NORTH ALONG THE COAST MONDAY...START TO MOVE
INLAND MONDAY NIGHT AND TUESDAY. THE MAIN FRONT IS FORECAST TO THEN
MOVE ONSHORE FROM THE WEST TUESDAY NIGHT INTO EARLY WEDNESDAY. THE
ASSOCIATED COOL UPPER TROUGH WILL CONTINUE TO BRING UNSETTLED WEATHER
OVER THE FORECAST AREA WEDNESDAY AND THURSDAY. EXPECT ANOTHER WARMING
AND DRYING TREND DEVELOPING BY THE WEEKEND.
&&

.SHORT TERM...AN UPPER HIGH THAT IS CENTERED OVER SOUTHWEST CANADA
BROUGHT WARM DRY WEATHER TO SOUTHWEST WASHINGTON AND NORTHWEST OREGON
TODAY AS TEMPS REACHED NEAR 80 BOTH INLAND AND AT THE COAST. OFFSHORE
WINDS AIDED THE WARM UP WITH A THERMAL TROUGH NEAR THE COAST. THE
ONLY RECORDS TIED OR BROKEN TODAY WERE 81 AT BOTH ASTORIA AND
NEWPORT.

EXPECT ONE MORE UNSEASONABLY WARM DAY MONDAY INLAND...BUT MOST
RECORDS ARE LIKELY OUT OF REACH EXCEPT PERHAPS AT TROUTDALE...
HILLSBORO...AND MCMINNVILLE.

CHANGES ARE COMING THOUGH. THE COAST SHOULD BE TURNING COOLER MONDAY
AS SOME MARINE AIR AND POSSIBLY SOME LOWER CLOUDS SPREAD NORTH DURING
THE DAY... WITH A DISTINCT SEA BREEZE IN THE AFTERNOON. SOUTHERLY
FLOW ALOFT AHEAD OF THE NEXT APPROACHING SYSTEM IS FORECAST TO SPREAD
MOISTURE AND INSTABILITY NORTHWARD THROUGH NORTHWEST OREGON AND
SOUTHWEST WASHINGTON LATER MONDAY AND ESPECIALLY MONDAY NIGHT.
ONSHORE FLOW INCREASES INLAND AS WELL BY TUESDAY SO THAT TUESDAY
SHOULD BE COOLER. MARINE CLOUDS MAY NOT BE VERY SOLID TUESDAY...WITH
THE MAIN CLOUDS BEING CONVECTIVE DEBRIS THAT COULD RESULT IN MORE
SHOWERS AND POSSIBLY A THUNDERSTORM AGAIN...THOUGH THE BEST CHANCE OF
THUNDER TUESDAY IS INCREASINGLY LOOKING LIKE THE HIGHER CASCADES.

THE FRONT ASSOCIATED WITH THE OFFSHORE SYSTEM IS FORECAST TO MOVE
ONSHORE TUESDAY NIGHT AND EARLY WEDNESDAY. THE FRONT DOES NOT LOOK
LIKE A REAL SOLID WINTER TYPE FRONT...SO IT LOOKS LIKE IT WILL MAINLY
INCREASE THE SHOWER COVERAGE OVER THE FORECAST AREA TUESDAY NIGHT AND
WEDNESDAY. THE ONSHORE FLOW LOOKS STRONG ENOUGH THAT THE CHANCE OF
THUNDER LOOKS PRETTY MINIMAL WEDNESDAY. TOLLESON

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...
WEDNESDAY NIGHT THROUGH SUNDAY. UPPER LEVEL TROUGH OVER THE EASTERN
PACIFIC JUST OFF THE NORTHERN CALIFORNIA COAST WILL REMAIN IN PLACE
THROUGH MUCH OF THE SECOND HALF OF THE WEEK BEFORE SLOWLY ADVANCING
INLAND INTO THE GREAT BASIN AND CUTTING OFF AS AN UPPER RIDGE NOSES
INTO THE PACIFIC NORTHWEST. SHOWERS SHOULD CONTINUE ACROSS THE AREA
ON THURSDAY...BUT TAPER OFF FOR MOST LOCATIONS ON FRIDAY AS THE
RIDGING BUILDS OVER THE REGION AND THE UPPER LOW MOVES FURTHER INTO
THE SOUTHWEST U.S. DID MAINTAIN SLIGHT CHANCE OF SHOWERS OVER THE
CASCADES HOWEVER...GIVEN BOTH THE POTENTIAL FOR SHOWERS TO WRAP
AROUND THE LOW AND SOME UNCERTAINTY IN THE EVOLUTION OF HOW FAR SOUTH
THE UPPER LOW MOVES. DAYTIME TEMPERATURES THURSDAY WILL BE CLOSER TO
SEASONAL NORMS...BEFORE WARMING INTO THE 70S INLAND AS HEIGHTS RISE
IN THE WARMING AIR MASS. CULLEN
&&

.AVIATION...EXPECT PRIMARILY VFR CONDITIONS AT ALL TAF SITES THROUGH
06Z TUESDAY AS OFFSHORE FLOW GIVES WAY TO INCREASING ONSHORE FLOW
LATE MONDAY. THE LONE EXCEPTION TO THIS WILL LIKELY BE AT KONP WHERE
MARINE STRATUS CURRENTLY NEAR THE BAY AREA OF CALIFORNIA WILL LIKELY
ARRIVE BETWEEN 00Z AND 06Z TUESDAY AND BRING A PERIOD OF IFR
CONDITIONS.

KPDX AND APPROACHES...EXPECT VFR CONDITIONS THROUGH 06Z TUESDAY AS
OFFSHORE FLOW DECREASES OVER THE REGION. /NEUMAN
&&

.MARINE...A SOUTHERLY WIND REVERSAL WILL WORK ITS WAY UP THE COAST
OVERNIGHT AND MONDAY WITH A PERIOD OF GUSTY 20 KT SOUTH WINDS. THERE
IS A CHANCE WINDS COULD SPIKE UP TO 25 KT BRIEFLY...BUT DO NOT THINK
IT WILL BE PROLONGED ENOUGH TO WARRANT A SMALL CRAFT ADVISORY FOR
WINDS. A WESTERLY SWELL SHOULD PUSH SEAS TEMPORARILY INTO THE 7 TO 9
FT RANGE ON MONDAY...BUT SEAS LOOK TO RELAX TUESDAY.

HIGH PRESSURE BUILDING BACK INTO THE NORTHEAST PACIFIC SHOULD BRING
NORTHERLY WINDS BACK ON TUESDAY WITH PERIODS OF GUSTY 25 TO 30 KT
NORTHERLY WINDS DURING THE SECOND HALF OF NEXT WEEK AND POSSIBLY NEXT
WEEKEND AS WELL...PARTICULARLY ACROSS THE CENTRAL OREGON WATERS.
WHILE SEAS SHOULD GENERALLY REMAIN UNDER 10 FT FOR MUCH OF THE NEXT
WEEK...EXPECT SEAS TO BECOME ESPECIALLY STEEP AND HAZARDOUS DURING
THE SECOND HALF OF THE WEEK AS SEAS BECOME FRESH SWELL/WIND DOMINATED
DUE TO PERIODS OF NORTH-NORTHWESTERLY GALES OFF VANCOUVER ISLAND.
/NEUMAN
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...NONE.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.



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